Hammer drill

ABSTRACT

A downhole apparatus connected to a workstring within a wellbore. The workstring is connected to a bit member. The apparatus includes a mandrel operatively connected to a downhole motor mechanism, an anvil member operatively formed on the bit member, the anvil member being operatively connected to the mandrel, a radial bearing housing unit operatively connected to the workstring, with the radial bearing housing unit being disposed about the mandrel, and a hammer member slidably attached to the radial bearing housing unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/065,532, filed on Oct. 17, 2014, which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to downhole tools. More particularly, but not byway of limitation, this invention relates to a downhole percussion tool.

In the drilling of oil and gas wells, a bit means is utilized to drill awellbore. Downhole percussion tools, sometimes referred to as hammers,thrusters, or impactors are employed in order to enhance the rate ofpenetration in the drilling of various types of subterranean formations.In some types of wellbores, such as deviated and horizontal wells,drillers may utilize downhole mud motors. The complexity and sensitivityof bottom hole assemblies affects the ability of drillers to use certaintools, such as downhole hammers.

SUMMARY OF THE INVENTION

In one embodiment, a downhole apparatus connected to a workstring withina wellbore is disclosed. The workstring is connected to a bit member.The apparatus comprises a power mandrel operatively connected to a motormeans; an anvil member operatively formed on the bit member, the anvilmember being operatively connected to the power mandrel; a radialbearing housing unit operatively connected to the workstring, with theradial bearing housing unit being disposed about the power mandrel; aspring saddle operatively attached to the radial bearing housing unit; aspring spacer disposed about the spring saddle; a spring having a firstend and a second end, with the first end abutting the spring saddle; ahammer member slidably attached to the spring saddle, and wherein thehammer member abuts the second end of the spring. In one preferredembodiment, the hammer and the anvil is below the radial bearing housingunit. The workstring may be a tubular drill string, or coiled tubing orsnubbing pipe. The anvil member contains a radial cam face having aninclined portion and a upstanding portion. The hammer member contains aradial cam face having an inclined portion and a upstanding portion.

In another embodiment, a downhole apparatus is connected to a workstringwithin a wellbore, with the downhole apparatus connected to a bitmember. The apparatus comprises a mandrel operatively connected to amotor means; an anvil operatively formed on the bit member, with theanvil being operatively connected to the mandrel; a radial bearinghousing unit operatively connected to the workstring, with the radialbearing housing unit being disposed about the mandrel; and a hammerslidably attached to the radial bearing housing unit. In one embodiment,the hammer and the anvil is below the radial bearing housing unit. Theanvil contains a cam face having an inclined portion and an upstandingportion, and the hammer contains a cam face having an inclined portionand a upstanding portion. The apparatus may optionally further include aspring saddle operatively attached to the radial bearing housing unit;and, a spring spacer disposed about the spring saddle, with a springhaving a first end and a second end, with the first end abutting thespring spacer. In one embodiment, the hammer is slidably attached to theradial bearing housing unit with spline means operatively positioned onthe spring saddle.

Also disclosed in one embodiment, is a method for drilling a wellborewith a workstring. The method includes providing a downhole apparatusconnected to the workstring within a wellbore, the apparatus beingconnected to a bit member, the downhole apparatus comprising: a powermandrel operatively connected to a motor means, thereby providing torqueand rotation from the motor to the bit via the power mandrel, an anvilmember operatively formed on the bit member, the anvil member beingoperatively connected to the power mandrel; a radial bearing housingunit operatively connected to the workstring, with the radial bearinghousing unit being disposed about the power mandrel; a spring saddleoperatively attached to the radial bearing housing unit; a spring spacerdisposed about the spring saddle, a spring having a first end and asecond end, with the first end abutting the spring-spacer; a hammermember slidably attached to the spring saddle, and wherein the hammermember abuts the second end of the spring. The method further includeslowering the workstring into the wellbore; contacting the bit memberwith a subterranean interface (such as reservoir rock); engaging adistal end of the power mandrel with an inner surface of the bit member;slidably moving the anvil member; and, engaging a radial cam surface ofthe anvil member with a reciprocal radial cam surface of the hammermember so that the hammering member imparts a hammering (sometimesreferred to as oscillating) force on the anvil member.

In one disclosed embodiment, when activating the motor (pumping fluid),the power mandrel, the drive shaft and the bit box sub are spinning thebit. If the hammermass cam surface and the anvil cam surface areengaged, the hammering (i.e. percussion) is activated and adds anoscillating force to the bitbox sub. Thus, the bit will be loaded withthe static weight on bit from the drill string and the added oscillatingforce of the impacting hammermass. If the hammermass cam surface and theanvil cam surface are disengaged, the bitbox sub is only rotating.

A feature of the disclosure is that the spring means is optional. Withregard to the spring embodiment, the type of spring used may be a coiledspring or Belleville spring. An aspect of the spring embodiment includesif the hammermass cam surface and the anvil cam surface are engaged andthe hammermass is sliding axially relative to the anvil member, thespring means will be periodically compressed and released thusperiodically accelerating the hammermass towards the anvil member thatin turn generates an additional impact force. A feature of the springembodiment is the spring adjusted resistance without moving the mandrelrelative to the housing. Another feature of one embodiment is themandrel is defined by supporting the axial and radial bearings. Anotherfeature of one embodiment is that the hammer mechanism can be locatedbetween the bit and the motor or below the bearing section and themotor.

As per the teachings of the present disclosure, yet another featureincludes that the motor means turns and hammers (i.e. oscillating force)when drilling fluid is pumped through the motor and both cam faces areengaged. Another feature is the motor only turns when drilling fluid ispumped through the motor and both cam faces are disengaged. The motordoes not turn nor hammers when no drilling fluid is pumped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional view of a first embodiment of the downholeapparatus.

FIG. 2 is a partial sectional view of lower housing of the downholeapparatus of the first embodiment in the engaged mode.

FIG. 3 is a partial sectional view of the lower housing of the downholeapparatus of the first embodiment in the disengaged mode.

FIG. 4 is a partial sectional view of the downhole apparatus of thefirst embodiment as part of a bottom hole assembly.

FIG. 5 is a partial sectional view of lower housing of the downholeapparatus of a second embodiment in the engaged mode.

FIG. 6 is a partial sectional view of the lower housing of the downholeapparatus of the second embodiment in the disengaged mode.

FIG. 7A is perspective view of one embodiment of the anvil radial cammember.

FIG. 7B is a top view of the anvil radial cam member seen in FIG. 7A.

FIG. 8 is a perspective view of one embodiment of the hammer radial cammember.

FIG. 9 is a schematic depicting the downhole apparatus of the presentinvention in a wellbore.

FIG. 10A is a graph of static weight on bit (WOB) versus time duringdrilling operations.

FIG. 10B is a graph of dynamic WOB utilizing a percussion unit.

FIG. 10C is a graph of dynamic WOB utilizing percussion unit, whereinthe impact force is overlaid relative to the static load.

FIG. 11 is a partial sectional view of an alternate embodiment of thelower housing of the downhole apparatus.

FIG. 12 is a partial sectional view of another alternate embodiment ofthe lower housing of the downhole apparatus.

FIG. 13 is a partial sectional view of a further alternate embodiment ofthe lower housing of the downhole apparatus.

FIG. 14 is a schematic view of the hammermass and anvil sub shown inFIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the FIG. 1, a partial sectional view of the downholeapparatus 2 of a first embodiment will now be discussed. The firstembodiment apparatus 2 includes a power mandrel, seen generally at 4,that is operatively attached to the output of a downhole mud motor (notshown). The apparatus 2 also includes a radial bearing housing unit,seen generally at 6. The radial bearing housing unit 6 will beoperatively attached to the workstring, such as drill pipe or coiledtubing, as will be described later in this disclosure. Moreparticularly, FIG. 1 shows the power mandrel 4 (which is connected tothe output of the motor section, as is well understood by those ofordinary skill in the art). The mandrel 4 may be referred to as thepower mandrel or flex shaft. Also shown in FIG. 1 is the upper bearinghousing 10 a which includes the upper radial bearings 12 a, lower radialbearing 14 a, balls 16 a and thrust races 18 a. The lower housing isseen generally at 20 a in FIG. 1 and will be described in furtherdetail.

As seen in FIG. 1, a partial sectional view of lower housing 20 a of thedownhole apparatus 2 of the first embodiment is shown. FIG. 1 depictsthe hammermass 22 a (sometimes referred to as the hammer member orhammer), which is attached (for instance, by spline means via a springsaddle 40 a) to the radial bearing housing unit 6. The hammermass 22 awill have a radial cam surface 24 a. The hammermass 22 a will engagewith the anvil 26 a, wherein the anvil 26 a has a first end thatcontains a radial cam surface 28 a, wherein the radial cam surface 28 aand radial cam surface 24 a are reciprocal and cooperating in thepreferred embodiment, as more fully set out below. FIG. 1 also depictsthe power mandrel 4, which is fixed connected to the driveshaft 30 a viathread connection or similar means. A key 32 a (also referred to as aspline) allows for rotational engagement of the power mandrel 4 and thedriveshaft 30 a with the bitbox sub 34 a, while also allowing forlateral movement of the bitbox sub 34 relative to the drive shaft 30 a.The anvil 26 a is fixedly connected to the bitbox sub 34 a.

FIG. 1 also depicts the spring means 36 for biasing the hammermass 22 a.The spring means 36 is for instantaneous action. More specifically, FIG.1 depicts the spring saddle 40 a that is an extension of the bearinghousing 6 i.e. the spring saddle 40 a is attached (via threads forinstance) to the bearing housing 6. The spring saddle 40 a is disposedabout the driveshaft 30 a. Disposed about the spring saddle 40 a is thespacer sub 42 a, wherein the spacer sub 42 a can be made at a variablelength depending on the amount of force desired to load the spring means36. As shown, the spring means 36 is a coiled spring member. The springmeans 36 may also be a Belleville washer spring. One end of the springmeans 36 abuts and acts against the hammermass 22 a which in turn urgesto engagement with the anvil 26 a.

In FIG. 2, a partial sectional view of the lower housing 20 a of thedownhole apparatus 2 of the first embodiment in the engaged mode isshown. It should be noted that like numbers appearing in the variousfigures refer to like components. The cam surface 24 a and cam surface28 a are abutting and are face-to-face. Note the engaged position of theend 37 a of the driveshaft 30 a with the angled inner surface 38 a ofthe bitbox sub 34 a securing the axial transmission of the WOB from thedrillstring to the bitbox sub 34 a and the bit (not showing here). InFIG. 3, a partial sectional view of the lower housing 20 a of thedownhole apparatus 2 of the first embodiment in the disengaged mode willnow be described. In this mode, the apparatus 2 can be, for instance,running into the hole or pulling out of the hole, as is well understoodby those of ordinary skill in the art. Therefore, the radial cam surface24 a of hammer 22 a is no longer engaging the radial cam surface 28 a ofthe anvil 26 a. Note the position of the end 37 a of the driveshaft 30 ain relation to the angled inner surface 38 a of the bitbox sub 34 a. Asstated previously, the bit member (not shown in this view) is connectedby ordinary means (such as by thread means) to the bitbox sub 34 a.

Referring now to the FIG. 4, a schematic view of the downhole apparatus2 of the first embodiment will now be discussed as part of a bottom holeassembly. The first embodiment the apparatus 2 includes the powermandrel, seen generally at 4, that is operatively attached to the outputof a downhole mud motor “MM”. The apparatus 2 also includes a radialbearing housing unit, seen generally at 6. The radial bearing housingunit 6 will be operatively attached to the workstring 100, such as drillpipe or coiled tubing. Also shown in FIG. 4 is the upper bearing housing10 a which includes the upper radial bearings 12 a, lower radial bearing14 a, balls 16 a and thrust races 18 a. The lower housing is seengenerally at 20 a. As shown in FIG. 4, the bit 102 is attached to theapparatus 2, wherein the bit 102 will drill the wellbore as readilyunderstood by those of ordinary skill in the art.

FIG. 5 and FIG. 6 depict the embodiment of the apparatus 2 without thespring means. Referring now to FIG. 5, a partial sectional view of lowerhousing 20 b of the downhole apparatus 2 of a second embodiment in theengaged mode is shown. FIG. 5 depicts the hammermass 22 b (sometimesreferred to as the hammer member or hammer), which is attached (forinstance, by spline means) to the spring saddle and the radial bearinghousing unit (not shown here). The hammermass 22 b will have a radialcam surface 24 b. The hammermass 22 b will engage with the anvil 26 b,wherein the anvil 26 b has a first end that contains a radial camsurface 28 b, wherein the radial cam surface 28 b and radial cam surface24 b of the hammermass 22 b are reciprocal and cooperating in thepreferred embodiment, as more fully set out below. FIG. 5 also depictsthe driveshaft 30 b (with the driveshaft 30 b being connected to thepower mandrel, not shown here). A key 32 b (also referred to as aspline) allows for rotational engagement of the drive shaft 30 b withthe bitbox sub 34 b, while also allowing for lateral movement of thebitbox sub 34 b relatively to the driveshaft 30 b-. The anvil 26 b isfixed connected to the bitbox sub 34 b.

In FIG. 6, a partial sectional view of the lower housing 20 b of thedownhole apparatus 2 of the second embodiment in the disengaged modewill now be described. In this mode, the apparatus 2 can be, forinstance, running into the hole or pulling out of the hole, as wellunderstood by those of ordinary skill in the art. Hence, the radial camsurface 24 b of hammermass 22 b is no longer engaging the radial camsurface 28 b of the anvil 26 b. Note the position of the end 37 b of thedriveshaft 30 b in relation to the angled inner surface 38 b of thebitbox sub 34 b. As previously mentioned, a bit member is connected(such as by thread means) to the bitbox sub 34 b.

Referring now to FIG. 7A, a perspective view of one embodiment of theanvil radial cam member. More specifically, FIG. 7A depicts the anvil 26a having the radial cam surface 28 a, wherein the radial cam surface 28a includes an inclined portion 50, horizontal (flat) portion 51, and anupstanding portion 52. The inclined portion 50 may be referred to as aramp that leads to the vertical upstanding portion 52 as seen in FIG.7A. FIG. 7B is a top view of the anvil radial cam member seen in FIG.7A. In one embodiment, multiple ramps (such as inclined portion 50,horizontal portion 51, extending to an upstanding portion 52) can beprovided on the radial cam surface 26 a.

In FIG. 8, a perspective view of one embodiment of the hammer radial cammember is depicted. More specifically, FIG. 8 shows the hammermass 22 athat has a radial cam surface 24 a. The radial cam surface 24 a also hasan inclined portion 54, horizontal (flat) portion 55 and an upstandingportion 56, which are reciprocal and cooperating with the inclinedportion and upstanding portion of the anvil radial cam surface 28 a, asnoted earlier. Note that the cam means depicted in FIGS. 7A, 7B and 8will be the same cam means for the second embodiment of the apparatus 2illustrated in FIGS. 5 and 6.

A schematic of a drilling rig 104 with a wellbore extending therefrom isshown in FIG. 9. The downhole apparatus 2 is generally shown attached toa workstring 100, which may be a drill string, coiled tubing, snubbingpipe or other tubular. The bit member 102 has drilled the wellbore 106as is well understood by those of ordinary skill in the art. Thedownhole apparatus 2 can be used, as per the teachings of thisdisclosure, to enhance the drilling rate of penetration by use of apercussion effect with the hammer 22 a/22 b impacting force on the anvil26 a/26 b, previously described. In one embodiment, the downhole hammeris activated by the bit member 102 coming into contact with a reservoirinterface, such as reservoir rock 108 found in subterranean wellbores orother interfaces, such as bridge plugs. In one embodiment, a driller candrill and hammer at the same time. As per the teachings of thisinvention, in the spring (first) embodiment, the hammermass will beaccelerated by a spring force of the compressed spring thus generatingan impact force when the hammermass hits the anvil member.

Referring now to FIGS. 10A, 10B and 10C, graphs of the weight on bit(WOB) versus time during drilling operations will now be discussed. Morespecifically, FIG. 10A is the static WOB versus time; FIG. 10B is adynamic WOB utilizing the hammer and anvil members (i.e. percussionunit); and, FIG. 10C represents—the summarized WOB wherein the impactforce is graphically overlaid (i.e. summation) relative to the staticload, in accordance with the teachings of this disclosure. As notedearlier, the percussion unit is made-up of the anvil, hammer, cam shaftarrangement and spring. The wave form W depicted in FIGS. 10B and 10Crepresent the oscillating impact force of the percussion unit duringuse. Note that in FIG. 10C, W1 represents the force when the hammermassimpacts the anvil and W2 represents the force when the hammermass doesnot impact the anvil. It must be noted that the size and shape of thewave form can be diverse depended on the material and the design of thespring, the anvil, the hammermass and the spacer sub.

An aspect of the disclosure is that the static weight of the drillstring is transmitted different to the bit than the impact force(dynamic weight on bit) created by the hammer and anvil member. Thestatic WOB is not transmitted through the hammer and anvil membersincluding cam surface (i.e. cam shaft arrangement). The impact force istransmitted through the hammer and anvil to the bit and not through thecamshaft arrangement. The percussion unit will generate the impact forceif the cam shafts arrangements are engaged independently of the amountof WOB. Yet another aspect of one embodiment of the disclosure is thepower section of the motor is simultaneously rotationally driving thebit and axially driving the hammer member. No relative axial movement istaking place between the housing of the apparatus and the inner drivetrain (including the power mandrel and the driveshaft) that is drivingthe bit and the percussion unit.

Another aspect of the one embodiment is the anvil is positioned as closeas possible to the bit; the bit box and/or bit can function as an anvil.Still yet another aspect of one embodiment is that when the bit does notencounter a resistance, no interaction between the two cams isexperienced and thus no percussion motion.

FIG. 11 illustrates an alternate embodiment of lower housing 20 c withspring saddle 40 c disposed about driveshaft 30 c. Spring means 36 c isdisposed about spring saddle 40 c. One end of spring means 36 c abutsand acts against hammermass 22 c while the other end of spring means 36c abuts and acts against spacer sub 42 c. Anvil sub 150 is also disposedabout driveshaft 30 c. Anvil sub 150 is fixedly connected to bitbox sub34 c. Key 151 may rotationally lock bitbox sub 34 c to driveshaft 30 c,while allowing axial movement of bitbox sub 34 c and anvil sub 150relative to driveshaft 30 c. Rolling element 152 may be disposed inpartial cavity 154 inside of anvil sub 150. This apparatus may includeany number of rolling elements 152. The number of rolling elements,however, should not exceed the number of high points or ramp portions onradial cam surface 24 c. In one embodiment, the number of rollingelements 152 may be equal to the number of high points or the number orramp portions on radial cam surface 24 c (described in more detailbelow). The rolling elements 152 may be equally spaced along thecircumference of the anvil sub 150 and the radial cam surface 24 c. Inanother embodiment, partial cavity 154 may be in an inner wall of anvilsub 150. Anvil sub 150 may include three partial cavities 154 eachdimensioned to retain rolling elements 152. Anvil sub 150 may includeany number of partial cavities 154 for housing rolling elements 152.Partial cavities 154 contain rolling elements 152 while allowingrotation of rolling elements 152 within the cavities. Rolling elements152 may be spherical members, elongated spherical members, cylindricalmembers, other convex members, or concave members. In one embodiment,the spherical elements are stainless steel ball bearings or ceramicballs. Wear ring 156 may be disposed within anvil sub 150 adjacent topartial cavities 154 and rolling elements 152. As anvil sub 150 rotateswith the rotation of driveshaft 30 c, rolling elements 152 roll alongradial cam surface 24 c of hammermass 22 c thereby creating an axialdisplacement of hammermass 22 c relative to anvil sub 150 until rollingelements 152 roll over an upstanding portion of radial cam surface 24 ccreating an axial impact as spring 36 c forces hammermass 22 c towardanvil sub 150.

FIG. 12 illustrates another alternate embodiment of lower housing 20 cincluding anvil sub 160. Anvil sub 160 may be fixedly connected tobitbox sub 34 c, which is rotationally locked to driveshaft 30 c.Rolling element 152 may be disposed in partial cavity 162 in an innerwall of anvil sub 160. Anvil sub 160 may include any number of partialcavities 162 for housing rolling elements 152. For example, anvil sub160 may include three partial cavities 162. Anvil sub 160 may includethrust race 164 adjacent to partial cavities 162 and rolling elements152. A plurality of thrust bearings 166 are disposed between thrust race164 and radial shoulder 168 of anvil sub 160. Radial shoulder 168 mayinclude a groove configured to retain thrust bearings 166, such as ballbearings. Thrust bearings 166 and thrust race 164 rotate relative toanvil sub 160 as rolling elements 152 roll along the circumference ofradial cam surface 24 c. Thrust bearings 166 and thrust race 164 assistin ensuring that rolling elements 152 roll (as opposed to sliding) overradial cam surface 24 c of hammermass 22 c.

FIG. 13 illustrates a further embodiment of lower housing 20 c includinganvil sub 170. Anvil sub 170 may be fixedly connected to bitbox sub 34c, which is rotationally locked to driveshaft 30 c. Anvil sub 170 mayinclude one or more partial cavities 172 in its inner wall. Innerhousing 176 is disposed within anvil sub 170 Inner housing 176 mayinclude a lateral groove dimensioned to retain rolling elements 152 inconnection with partial cavities 172 of anvil sub 170. In this way,anvil sub 170 and inner housing 176 may securely retain rolling elements152. Connecting element 200 locks anvil sub 170 to inner housing 176.Connecting element 200 may include set screws, pins, splines, or keys.Alternatively, instead of partial cavities 172 in anvil sub 170 andinner housing 176, a separate cage member may be placed in anvil sub 170to retain rolling elements 152. Anvil sub 170 may also include thrustrace 178 and a plurality of thrust bearings 180 disposed between thrustrace 178 and radial shoulder 182 of anvil sub 170. FIG. 13 shows hammersurface 182 on hammermass 22 c and anvil surface 184 on anvil sub 170.Hammermass 22 c also includes splines 186 that cooperate with splines onspring saddle 40 c to allow hammermass 22 c to move axially whilepreventing hammermass 22 c from rotating relative to spring saddle 40 c.As anvil sub 150 rotates with the rotation of driveshaft 30 c, rollingelements 152 roll along radial cam surface 24 c of hammermass 22 cthereby creating an axial displacement of hammermass 22 c relative toanvil sub 150 until rolling elements 152 roll over upstanding portionsof radial cam surface 24 c creating an axial impact by hammer surface182 impacting anvil surface 184. This arrangement increases thelongevity of the apparatus by reducing wear associated with impactforces on rolling elements 152 and radial cam surface 24 c. Thisapparatus may include a mechanism for disabling the impacts ofhammermass 22 c to anvil sub 170, such as by disengaging spring 36 cfrom hammermass 22 c, by disengaging splines 186 of hammermass 22 c, orby locking hammermass 22 c to anvil sub 170.

FIG. 14 is a schematic view of the interaction between variouscomponents of hammermass 22 c and anvil sub 170 shown in FIG. 13. Radialcam surface 24 c of hammermass 22 c may include ramp portion 188 leadingfrom low point 189 to high point 190, which is adjacent to upstandingportion 192. This profile pattern may repeat along the circumference ofradial cam surface 24 c. As anvil sub 170 rotates with the rotation ofdriveshaft 30 c, rolling elements 152 roll along radial cam surface 24 cof hammermass in direction 210. Specifically, rolling elements 152 mayroll along ramp 188 to high point 190. This interaction axiallydisplaces hammer surface 182 of hammermass 22 c away from anvil surface184 of anvil sub 170. When rolling elements 152 roll past high point190, rolling elements 152 may disengage radial cam surface 24 c andhammermass 22 c may be forced axially toward anvil sub 170 due to theforce of spring 36 c. Hammer surface 182 impacts anvil surface 184providing an impact force to the drill bit. FIG. 14 shows theconfiguration of these components at the moment of impact between hammersurface 182 and anvil surface 184. At the moment of impact, rollingelements 152 may not in contact with radial cam surface 24 c due to theaxial clearance D₁ between a diameter D₂ of the rolling elements 152 andthe distance D₃ between thrust race 178 and low point 189 of radial camsurface 24 c. Axial clearance D₁ may further reduce wear on rollingelements 152 and radial cam surface 24 c. FIG. 14 also shows the totalstroke length, i.e., the length of axial displacement of hammermass 22 cbetween subsequent impacts. In an alternate embodiment, the rollingelements are housed within the hammermass and the anvil sub includes theradial cam surface.

It will be apparent to one skilled in the art that modifications may bemade to the illustrated embodiments without departing from the spiritand scope of the invention. Insofar as the description above and theaccompanying drawing disclose any additional subject matter that is notwithin the scope of the claims below, the inventions are not dedicatedto the public and right to file one or more applications to claim suchadditional inventions is reserved.

We claim:
 1. An apparatus for generating an axial impact, comprising: ahammer segment having a radial cam surface; an anvil segment having aninternal radial shoulder, an inner wall extending from the internalradial shoulder, and one or more partial cavities adjacent to theinternal radial shoulder in an internal space within the inner wall ofthe anvil segment; one or more rolling elements partially disposedwithin the partial cavities of the anvil segment, wherein the rollingelements cooperate with the radial cam surface of the hammer segment foraxially displacing the hammer segment from the anvil segment andgenerating the axial impact upon rotation of the hammer segment or theanvil segment, wherein each rolling element moves 360 degrees relativeto the hammer segment.
 2. The apparatus of claim 1, wherein the radialcam surface of the hammer segment contacts the internal radial shoulderof the anvil segment to generate the axial impact upon rotation of thehammer segment or the anvil segment.
 3. The apparatus of claim 1,wherein the hammer segment further comprises a hammer surface and theanvil segment comprises an anvil surface.
 4. The apparatus of claim 3,wherein the hammer surface is a radial surface and the anvil surface isa radial surface.
 5. The apparatus of claim 4, wherein the hammersurface contacts the anvil surface to generate the axial impact uponrotation of the hammer segment or the anvil segment.
 6. The apparatus ofclaim 5, wherein the hammer surface is disposed around the radial camsurface of the hammer segment.
 7. The apparatus of claim 6, wherein thehammer surface is separated from the radial cam surface by an axiallength.
 8. The apparatus of claim 6, wherein the anvil surface isdisposed on an exterior surface of the anvil segment.
 9. The apparatusof claim 8, wherein the radial cam surface of the hammer segment isdisposed within the inner wall of the anvil segment.
 10. The apparatusof claim 2, wherein the partial cavities are on the inner wall of theanvil segment.
 11. The apparatus of claim 3, further comprising a wearring disposed within the internal space of the anvil segment adjacent tothe internal radial shoulder, wherein the wear ring is in contact withthe rolling elements.
 12. The apparatus of claim 3, further comprising athrust race and a plurality of thrust bearings disposed within theinternal space of the anvil segment, wherein the plurality of thrustbearings are disposed between the internal radial shoulder and thethrust race, and wherein the thrust race is in contact with the rollingelements.
 13. The apparatus of claim 12, wherein the thrust race rotatesrelative to the anvil segment as the rolling elements engage the radialcam surface of the hammer segment.
 14. The apparatus of claim 13,further comprising an internal housing disposed within the internalspace of the anvil segment, said internal housing including a partialcavity dimensioned to partially house one of the rolling elements sothat the rolling element is retained between the inner wall of the anvilsegment and the internal housing.
 15. The apparatus of claim 14, whereinthe radial cam surface of the hammer segment is disposed between theinner wall of the anvil segment and the internal housing.
 16. Theapparatus of claim 3, wherein the rolling elements are not in contactwith the radial cam surface when the hammer surface is in contact withthe anvil surface.
 17. The apparatus of claim 16, wherein the rollingelements are equally spaced along the circumference of the radial camsurface of the hammer segment.
 18. The apparatus of claim 3, wherein theradial cam surface of the hammer segment includes a tapered portion. 19.The apparatus of claim 18, wherein the tapered portion includes a ramp.20. The apparatus of claim 18, wherein the tapered portion includes anundulating waveform profile.
 21. An apparatus for generating an axialimpact, comprising: an anvil segment having a radial cam surface; ahammer segment having an internal radial shoulder, an inner wallextending from the internal radial shoulder, and one or more partialcavities adjacent to the internal radial shoulder in an internal spacewithin the inner wall of the hammer segment; one or more rollingelements partially disposed within the partial cavities of the hammersegment, wherein the rolling elements cooperate with the radial camsurface of the anvil segment for axially displacing the anvil segmentfrom the hammer segment and generating the axial impact upon rotation ofthe hammer segment or the anvil segment, wherein each rolling elementmoves 360 degrees relative to the anvil segment.
 22. A downholeapparatus connected to a workstring within a wellbore, said workstringbeing connected to a bit member having a motor means comprising: a powermandrel operatively connected to the motor means; an anvil memberoperatively formed on the bit member, said anvil member beingoperatively connected to said power mandrel, said anvil member includingan internal radial shoulder, an inner wall extending from the internalradial shoulder, and one or more partial cavities adjacent to theinternal radial shoulder in an internal space; one or more rollingelements partially disposed within the partial cavities of the anvilmember; a radial bearing housing unit operatively connected to theworkstring, with the radial bearing housing unit being disposed aboutsaid power mandrel; a spring saddle operatively attached to the radialbearing housing unit; a spring spacer disposed about said spring saddle;a spring having a first end and a second end, with the first endabutting the spring saddle; a hammer member slidably attached to saidspring saddle and abutting the second end of the spring, the hammermember including a radial cam surface that cooperates with the rollingelements disposed in the anvil member for axially displacing the hammermember from the anvil member and generating an axial impact uponrotation of the anvil member.
 23. The apparatus of claim 22, whereinsaid hammer member and said anvil member are below the radial bearinghousing unit.
 24. The apparatus of claim 23, wherein the workstring is atubular drill string or a coiled tubing string.
 25. The apparatus ofclaim 22, wherein the hammer member further comprises a hammer surfaceand the anvil member further comprises the anvil surface, and whereinhammer surface contacts the anvil surface to generate the axial impactupon rotation of the anvil member.
 26. The apparatus of claim 25,wherein the partial cavities are on the inner wall of the anvil member.27. The apparatus of claim 25, wherein the radial cam surface of thehammer member is disposed within the inner wall of the anvil member. 28.The apparatus of claim 25, further comprising a thrust race and aplurality of thrust bearings disposed within the internal space of theanvil member, wherein the plurality of thrust bearings are disposedbetween the internal radial shoulder and the thrust race, wherein thethrust race is in contact with the rolling elements, and wherein thethrust race rotates relative to the anvil member as the rolling elementsengage the radial cam surface of the hammer member.
 29. The apparatus ofclaim 28, further comprising an internal housing disposed within theinternal space of the anvil member, said internal housing including apartial cavity dimensioned to partially house one of the rollingelements so that the rolling element is retained between the inner wallof the anvil member and the internal housing, and wherein the radial camsurface of the hammer member is disposed between the inner wall and theinternal housing of the anvil member.
 30. A downhole apparatus connectedto a workstring within a wellbore, said workstring being connected to abit member with a motor means comprising: a power mandrel operativelyconnected to the motor means; an anvil member operatively formed on thebit member, said anvil member being operatively connected to said powermandrel, said anvil member including an internal radial shoulder, aninner wall extending from the internal radial shoulder, and one or morepartial cavities adjacent to the internal radial shoulder in an internalspace; one or more rolling elements partially disposed within thepartial cavities of the anvil member; a radial bearing housing unitoperatively connected to the workstring, with the radial bearing housingunit being disposed about said power mandrel; a hammer member slidablyattached to said radial bearing housing unit, the hammer memberincluding a radial cam surface that cooperates with the rolling elementsdisposed in the anvil member for axially displacing the hammer memberfrom the anvil member and generating an axial impact upon rotation ofthe anvil member.
 31. The apparatus of claim 30, wherein said hammermember and said anvil member are below the radial bearing housing unit.32. The apparatus of claim 30, wherein the workstring is a tubular drillstring or a coiled tubing string.
 33. The apparatus of claim 30, whereinthe hammer member further comprises a hammer surface and the anvilmember further comprises an anvil surface, and wherein hammer surfacecontacts the anvil surface to generate the axial impact upon rotation ofthe anvil member.
 34. The apparatus of claim 33, wherein the partialcavities are on the inner wall of the anvil member.
 35. The apparatus ofclaim 33, wherein the radial cam surface of the hammer member isdisposed within the inner wall of the anvil member.
 36. The apparatus ofclaim 33, further comprising a thrust race and a plurality of thrustbearings disposed within the internal space of the anvil member, whereinthe plurality of thrust bearings are disposed between the internalradial shoulder and the thrust race, wherein the thrust race is incontact with the rolling elements, and wherein the thrust race rotatesrelative to the anvil member as the rolling elements engage the radialcam surface of the hammer member.
 37. The apparatus of claim 36, furthercomprising an internal housing disposed within the internal space of theanvil member, said internal housing including a partial cavitydimensioned to partially house one of the rolling elements so that therolling element is retained between the inner wall of the anvil memberand the internal housing, and wherein the radial cam surface of thehammer member is disposed between the inner wall and the internalhousing of the anvil member.
 38. The apparatus of claim 30, wherein theapparatus further comprises: a spring saddle operatively attached to theradial bearing housing unit; a spring spacer disposed about said springsaddle; a spring having a first end and a second end, with the first endabutting the spring saddle.
 39. The apparatus of claim 38, wherein saidhammer member is slidably attached to said radial bearing housing unitwith spline means operatively positioned on said spring saddle.
 40. Theapparatus of claim 38, wherein the hammer member is located between thebit and the motor means.
 41. The apparatus of claim 38, wherein thehammer member is located below the bearing section of the apparatus. 42.A method for drilling a wellbore with a workstring, comprising: a)providing a downhole apparatus connected to the workstring within thewellbore, said apparatus being connected to a bit member, the downholeapparatus comprising: a power mandrel operatively connected to a motormeans; an anvil member with a radial cam surface operatively formed onthe bit member, said anvil member being operatively connected to saidpower mandrel, said anvil member including an internal radial shoulder,an inner wall extending from the internal radial shoulder, and one ormore partial cavities adjacent to the internal radial shoulder in aninternal space; one or more rolling elements partially disposed withinthe partial cavities of the anvil member; a radial bearing housing unitoperatively connected to the workstring, with the radial bearing housingunit being disposed about said power mandrel; a spring saddleoperatively attached to the radial bearing housing unit; a spring spacerdisposed about said spring saddle, a spring having a first end and asecond end, with the first end abutting the spring saddle; a hammermember with a radial cam surface slidably attached to said spring saddleand abutting the second end of the spring, the hammer member including aradial cam surface; b) lowering the workstring into the wellbore; c)contacting the bit member with a reservoir interface; d) engaging adistal end of said power mandrel with a surface of said bit member; e)slidably moving the anvil member; f) engaging the radial cam surface ofthe hammer member with the rolling elements disposed in the anvil memberto axially displace the hammer member from the anvil member and togenerate an axial impact upon rotation of the anvil member, therebyimparting an impact force on the bit member.
 43. The method of claim 42,wherein the method further provides that static weight on the bit memberis transmitted to the bit member different than the impact force createdby the hammer and anvil member whereby the maximum force on the bitmember is the sum of the static weight on bit member and the impactforce created by the hammer and the anvil member
 44. The method of claim42, wherein the method further provides that independent of the amountof weight on the bit an oscillating impact force will be generated ifthe radial cam surface of the hammer member and the rolling elementsdisposed in the anvil member are engaging each other
 45. The method ofclaim 42, wherein the hammer member further includes a hammer surfaceand the anvil member further includes an anvil surface, and wherein themethod further provides that the impact force is transmitted through thehammer surface and the anvil surface.
 46. The method of claim 42,wherein the method further provides the power section of the motor issimultaneously rotationally driving the bit member and axially drivingthe hammer member.
 47. The method of claim 42, wherein no relative axialmovement is taking place between the housing of the apparatus and theinner drive train that is rotationally driving the bit member andaxially driving the hammer member.